Synchronized signal separating circuit for a recording and reproducing apparatus

Abstract

A synchronizing signal separating circuit comprises an input terminal for receiving a composite color video signal to be recorded at the time of a recording, and for receiving a time-division-multiplexed signal at the time of a reproduction, a measuring circuit for measuring a time interval between a time when a horizontal synchronizing signal within an input signal received through the input terminal assumes a first predetermined value and a time when the horizontal synchronizing signal assumes a second predetermined value, a memory circuit having various correcting data pre-stored therein, for producing one correcting data in accordance with the time interval measured by the measuring circuit, and a signal generating circuit for generating the separated horizontal synchronizing signal at a time position in accordance with the one correcting data which is produced from the memory circuit. The various correcting data are pre-stored in the memory circuit for each of various time intervals required for the horizontal synchronizing signal to reach the second predetermined value from the first predetermined value, and contain data for constantly generating a separated horizontal synchronizing signal at a time position which is approximately constant in each of the various time intervals.

What is claimed is: 
     
       1. A synchronizing signal separating circuit for a color video signal recording and reproducing apparatus which records a time-division-multiplexed signal on a recording medium, said time-division-multiplexed signal having a time base compressed luminance signal and one of two kinds of time base compressed color difference signals time-division-multiplexed within one horizontal scanning period and having the two kinds of time base compressed color difference signals time-division-multiplexed in line-sequence with the time base compressed luminance signal, said time base compressed luminance signal and said time base compressed color difference signal being subjected to a time base compression responsive to a clock pulse which is formed based on an output signal of said synchronizing signal separating circuit, said recording and reproducing apparatus reproducing said time-division-multiplexed signal from the recording medium, said reproduced time-division-multiplexed signal being subject to a time base expansion responsive to a clock pulse which is formed based on an output signal of said synchronizing signal separating circuit so as to obtain a reproduced luminance signal and a reproduced line-sequential color difference signal which are returned to an original time base, said time-division-multiplexed signal having an achromatic level signal time-division-multiplexed between said time base compressed luminance signal and one of said time base compressed color difference signals, said achromatic level signal having a level which is approximately in a center of a level range from a pedestal level to a white peak level of said time base compressed luminance signal, having a transmission period which alternately changes for every one horizontal scanning period and havng a period of two horizontal scanning periods, said synchronizing signal separating circuit comprising: an input terminal for receiving a composite color video signal to be recorded at the time of a recording, and for receiving said time-division-multiplexed signal at the time of a reproduction;   a horizontal synchronizing signal separating circuit for generating a signal by slicing a horizontal synchronizing signal within said time-division-multiplexed signal received through said input terminal at approximately one-half a peak value of the horizontal synchronizing signal;   pulse generating means for delaying the output signal of said horizontal synchronizing signal separating circuit and for generating a first pulse which exists at a such time position that a leading edge of said achromatic level signal exists within the width of said first pulse; and   detecting means supplied with said first pulse from said pulse generating means and the output signal of said horizontal synchronizing signal separating circuit for generating a second pulse in phase with a leading edge of said achromatic level signal, said second pulse being produced at the time of the reproduction as a separated horizontal synchronizing signal.   
     
     
       2. A synchronizing signal separating circuit as claimed in claim 1 in which said detecting means comprises a gate circuit for passing the output signal of said horizontal synchronizing signal separating circuit during a period corresponding to the pulse width of said first pulse received from said pulse generating means, a comparator for comparing levels of an output signal of said gate circuit and a reference signal having a level which is approximately one-half the peak value of said time-division-multiplexed signal, and a differentiating circuit for differentiating an output signal of said comparator and for generating said second pulse. 
     
     
       3. A synchronizing signal separating circuit as claimed in claim 1 which further comprises a switching circuit for selectively supplying the output signal of said horizontal synchronizing signal separating circuit to an output terminal of said synchronizing signal separating circuit at the time of the recording, and for selectively supplying said second pulse obtained from said detecting means to said output terminal of said synchronizing signal separating circuit at the time of the reproduction.